Of same place



(No 110191.) 2 Sheets-$11591; 1.

- W. W. DEAN. 1

. TELEPHONE SYSTEM. No. 577,101. 7 I Patented Feb. 16, 1897..

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(No Model.) 2-Sheets-Sheet 2'.

W. W. DEAN.

V TELEPHONE SYSTEM. No. 577,101. Patented Feb. 16,1897.

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UNITED STATES PATENT OFFICE.

WILLIAM IV. DEAN, OF ST. LOUIS, MISSOURI, ASSIGNOR TO THE BELL TELEPHONE COMPANY OF MISSOURI, OF SAME PLACE.

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 5'77,101,-dated February 16, 1897. Application filed September 19, 1896. Serial No. 606,344. (No model.)

To all whom it may concern..-

Be it known that I, WILLIAM W. DEAN, a

citizen of the United States, residing at the city of St. Louis, in the State of Missouri, have invented a certain new and useful Improvement in Telephone Systems, (Case No.

phone system, and has for its object to provide a steady and constant current for the microphone-transmitter.

When voltaic cells are employed at each subscribers station, considerable attention is required to keep them in proper working order, together. with frequent renewals of the elements. Telephone systems have been devised in which current for the subscribers microphone is supplied by a common battery at the central station. In telephone systems of this description an objection has been that owing to the varying lengths and inductive efiects of the circuits in which the microphones and primaries are included an equal, steady, and constant current for each instrument has been obtained with difficulty.

My invention comprises an electrothermal generator at the subscribers station which is designed to supply current for the microphone, the heat necessary for the operation of said electrothermal generator being pref- 'erably obtained by a heating-conductor placed in proximity thereto, said conductor being heated by the passage of an electric current from any convenient source.

In practice I prefer to employ a centralized battery common to all the subscribers, which may be brought into circuit with the heating-conductor upon the removal of the subscribers telephone from its hook. Variations in the current from the centralized battery which would render the current impracticable or useless for telephonic purposes would not perceptibly affect the steadiness in temperature of the heating-conductor, and consequently the current from the thermal generator would remain steady and constant.

In certain cases it may not be practicable nor desirable to employ a centralized battery for heating purposes, as described. In such a contingency any suitable heating medium may be employed to cause the operation of the thermal generator. heating-conductor may be used and included in an adjacent incandescent-light circuit by suitable contacts, which may be closed upon the removal of the telephone from its hook.

I will describe my invention more in detail For instance, the v by reference to the accompanying drawings,

in which Figure 1 is a diagram of a telephone system embodying my invention in which the subscribers microphone-transmitter is supplied with current from an individual electrothermal generator in circuit therewith. Fig. 2 shows an electrothermal generator as adapted for use in such a system, the heating-coil being indicated diagrammatically. Fig. 3 illustrates in diagram a subscribers station, a separate source of current being used to supply the heat necessary for the operation of the electrothermal generator.

Like letters indicate like parts throughout the several figures.

Referring to Fig. 1, A and B represent subscribers stations, and G a portion of the apparatus at the central station. The micro phone-transmitter a is included in'a local circuit with the primaryb of the induction-coil b and an electrothermal generator 0. A heatin g-coil c is provided to furnish the heat necessary for the operation of said electrothermal generator 0, one end of said heating-coil being connected to ground, the other end connected to the middle of a retardation-coil d, whose upper and lower halves d and d are connected, respectively, with conductor b the coil being thus placed in shunt to the secondary b and hand-telephone f, which are included in series in conductor If, the ends of which conductor terminate at contact-points e e of the telephone-hook e. The hook e and contact-plate a, mounted thereon, but insulated therefrom, are connected through limbs m and y, respectively, to line-springs gg of spring-jack g at the central station.

Plugs h h are provided, the tips h and sleeves It being connected together by cord strands 11 11 in the usual manner. Clearingout annunciators j j are included in cord strand i, being shunted, however, by non-inductive resistances 7c 71".

A retardation-coil Z is connected in a bridge between the cord strands t' i, to the middle point of which is connected a conductor m, which leads through battery it to ground. Contact-point of spring-jack 9, against which line-spring g normally rests, is con nected through line-indicator 0 to the conductor m at point 0, and thence to the battery 'n.

Then subscriber A, desiring a connection, lifts his telephone from its ho ok, current from battery '17 finds path from ground through conductor m to the point 0', indicator 0, contact g lin e-spring g limb y, contact-plate a, conductor b retardation-coil d, heating-coil c to ground. Upon the insertion of the plug by the operator circuit is broken at contact current from battery it now flowing from ground through conductor m to the middle point of retardation-coil Z, where it divides, flowing through the cord strands, tip and sleeve of the plug 71., line-springs g g limbs or: and 3 in multiple, contacts e 6 conductor b retardation-coil d, heating-coil c to ground. The current through the heating-coil raises it to such a temperature that the electrothermal generator begins to operate, furnishing current for the primary talking-circuit.

The operation of making connection at the central stat-ion is well known, and I do not, therefore, further describe it. It is evident that any suitable form of eleotrothermal generator may be employed, but the one which 1 preferably use in practicing my invention is composed of alternate strips 10 and p of bismuth and antimony placed in contact, as shown in Fig. 2, a heating-coil a being wound around all the strips upon one side of the thermal generator, the ends of the coil being adapted to be connected to a source of electric current.

Binding-posts q q are attached to the end. strips, from which wires lead off to the points of application.

Referring to Fig. 3, a source of current S is shown, which is adapted to be included in circuit with the heating-coil 0 upon the removal of telephone f from its hook c.

It is evident that various modifications may be made without departing from the spirit of my invention, and

I therefore claim as new and desire to secure by Letters Patent, with only those limitations expressed or by law implied in view of the state of the related arts, the following:

1. In a telephone, the combination with the subscribers microphone and primary of the induction-coil, of an electrothermal generator in circuit therewith, a heating-coil in proximity to said electrothermal generator, means for supplying current to said heatingcoil, and means for controlling the supply of current to said heating-coil.

2. In a telephone system, the combination with the subscribers microphone,and primary of the induction-coil, .of an electrothermal generator in circuit therewith, a heating-coil, a source of current-supply for said heatingcoil, and means, controlled by the movement of the telephone-hook, for including said source of current in circuit with said heatingcoil, substantially as described.

3. In a telephone system, the combination with the subscribers microphone and primary of the induction-coil, of an electrothcrmal generator in circuit therewith, a heating-coil, a source of current at the central station, and means for including said source of current in circuit with said heating-coil substantially as described.

4. In a telephone system, the combination with the subscribers microphone and primary of the induction-coil, of an eleotrothermal generator in circuit therewith, a heating-coil in circuit with the telephone-line, a springjack terminal for said telephone-line, a pin g and cord circuit at the central station, and a source of current included in said cord circuit, said source of current being placed in electrical communication with said heatingcoil upon the insertion of the plug into the spring-jack, substantially as described.

5. In a telephone apparatus, the combination of a telephone-receiver with a telephonetransmitter, an electrothermal generator i11- cluded in circuit with said transmitter, means for heating said electrothermal generator, and a switch-hook for the receiver adapted to control said mcans,snbstantially as described.

6. In a telephone apparatus, the combination of an induction-coil, with a telephonereceiver, a telephone-transmitter, an electrothermal generator included in circuit with said transmitter and the primary of the induction-coil, a heating-conductor placed in proximity to said generator, a source of current adapted to be included in circuit with said heating-conductor, and a switch-hook for the telephone-receiver adapted to control the continuity of the circuit including said source of current and heating-conductor, substantially as described.

7. In a telephone system, the combination of atelephone-line extending from the central.

office to a subscribers station with a source of electricity connected therewith at the cen tral office, an induction-coil at the subscribers station a thermal generator and a microphone-transmitter included in circuit with the primary of said induction-coil, and a conductor adapted toheat said generator connected with said telephone-line and source of electricity, substantially as described.

8. In a telephone apparatus, the combination of a telephone-receiver, with a telephonetransmitter, an electrothermal generator included in circuit with said transmitter,a heating-conductor adapted to heat said generator, a source of current adapted to be included in circuit with said conductor, and a switch-hook for the telephone-receiver adapted to'control the continuity of the circuit including said source of current and heating-conductor, substantially as described.

9. In a telephone system, the combination of a telephone-line extending from the central office to a subscribers station, with a telephone-transmitter at the subscribers station, and an electrothermal generator included in circuit therewith, a conductor adapted to supply heat to said generator included or adapted to be included in circuit with the telephoneline, and a source of current at the central office included or adapted to be included in circuit with said conductor, substantially as described.

10. In a telephone system, the combination of a telephone-line extending from the central office to a subscribers station, a transmitter at the subscribers station, and an electrothermal generator included in circuit therewith, a heating-conductor associated with said generator, and connected or adapted to be connected with the telephone-line,asource of current, and switching mechanism at the central oftice adapted to include said source of current in circuit with the telephone-line and said conductor, substantially as described.

11. In a telephone system, the combination of a telephone-line extending from the central oflicc to a substation, with a telephone-receiver in circuit with the telephone-line at the substation, an induction-coil at the substation, a transmitter and an electrotherrnal generator included in circuit with the primary coil of said induction-coil, a heating-conductor, a source of current and a telephone-hook for the telephone-receiver adapted to complete a circuit including said source of current and conductor, substantially as described.

12. In a telephone system, the combination of a plurality of subscribers stations each having a telephone-transmitter, with electrothermal generators, one in circuit with each transmitter, a common source of current, a conductor leading from said source of current to said subscribers stations, and heating-conductors, one at each subscribers station,in circuit with the aforesaid conductor and source of current and adapted to heat saidthermal generators, substantially as described.

13. In a telephone system, the combination of a plurality of subscribers stations each having a primary circuit including a transmitter, thermal generator and the primary helix of an induction-coil, a common source of current, a conductor leading from said source of current to said subscribers stations, and heating-conductors, one at each subscribcrs station in circuit with the aforesaid conductor and source of current and adapted to heat said thermal generators, substantially as described.

In witness whereof I hereunto subscribe my name this 16th day of September, A. D. 1896.

VILLIAM W. DEAN.

Witnesses:

GEORGE P. BARTON, GEORGE L. CRAGG. 

